A Response to Perfetti’s (1985) Chapter 9 of Reading Ability: “Dyslexia”
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| The Process of Reading and How It is Changed for Dyslexics According to Perfetti (1985) |
Summary
In
this chapter, Perfetti defines dsylexia, explores various theories concerning
its cause, and looks at various types of subgroups. Also, it is argued that reading ability is a
continuum, rather than there being sharp differences between low-readers and
dyslexics.
In
order to be considered dyslexic, a child must be of normal intelligence, and
must read at least two years below grade level.
However, there are problems with this definition because a reader in
second grade will have a hard time meeting the
two-years-or-more-below-grade-level criterion, and IQ measured on verbal items
may not be normal because these items will presumably show the same
deficiencies as found in reading measures.
Thus, nonverbal IQ scores should be used for classification, but they
aren’t always. A fundamental question
exists—are there major differences between low-ability readers and dyslexic
ones? What is the extent to which verbal
processing causes the ability differences for these disabled readers?
The
traditional view of dyslexics as posited by Orton (1925, 1937) is that there
are visual-spatial deficits, primarily illustrated by letter reversals in
reading/writing. So there has been a
search for a neurological basis for dsylexia.
Dyslexic children tend to make two kinds of letter reversals in reading,
sequence errors and letter orientation reversal, and both seem to be
independent of each other. However,
these errors may result from verbal factors rather than spatial ones.
Boder (1971, 1973) identified to subtypes
of dsylexia, the dsyphonetics and the dyseidetic. The dsyphonetic has a disability in phonetic
processes and can’t decode. The
dyseidetic has problems with perceiving whole words. Boder felt that there was a third subtype who
couldn’t decode or perceive gestalts.
However, research is ambivalent regarding these categories. There is a disproportionately high number of
dsyphonetics, and in many experiences, the two subtypes didn’t perform
differently on tasks of auditory or visual stimuli. Thus, there is movement in the field to
consider reading ability as a continuum.
Another explanation of subtype is the
left-brain right-brain schema which stipulates that the left hemisphere is
where linguistic and analytic processes occur, while nonlinguistic and holistic
processes occur in the right-brain.
Perhaps subtypes of reading disability occur at different stages of a
child learning to read because beginning readers use more right-brain processes
due to unfamiliar letter forms. As they
continue developing, the left-brain becomes more important because there are
more linguistic processes necessary in later reading.
Is
it possible that dyslexic readers suffer from the same deficiencies as
low-skilled readers in areas of decoding difficulty, lexical access, and
working memory limitations? Experiments
show that dyslexics don’t have rapid decoding skills, they are slower at rapid
automatized naming, and they have reduced working memories. As
Morrison suggests (1980) perhaps they have a general rule-learning issue. Perhaps dyslexics have a speech deficit,
either with nonactivation or deactivation of speech codes in memory or perhaps
they have differences in fundamental speech perception, as shown by the rhyming
effect. The differences in disability
seem to be differences of degree, eliminating the subtype model. Perhaps subtypes are used because they have
been seen with acquired dyslexics. But
it’s not clear that developmental dyslexia and acquired dsylexia are
comparable.
Response: My Questions
After reading this chapter, I am left with
several questions. Young
beginning readers do reverse letters and even numbers though they may not be
disabled. Why? Because the process is so new? My son, Gavin, 5 1/2, reverses b's and d's
and e's and 3's and s's. Should I be
worried? Why do dyslexic readers
overcompensate when they struggle with left hemisphere and have higher than
normal right-brain functions? Is this
comparable to a blind person with amplified hearing? As far as dyslexics perceiving three-letter words correctly but
having difficulty with four and five letter words presented foveally, is there
a relationship to visual perception of the print? This reminds me of the lady in our class
who's husband had a stroke. With the
rhyming effect, I was surprised. It seems
to me that rhyming letters would be easier to recall, like word families
(patterns) are easier to spell and decode because they're predictable. Of course, because these letters sound
similar, maybe that would create the confusion due to less
"boundaries" between the sounds of letters. Because dyslexics have
less well-defined speech perception, they didn’t struggle more with rhymed
letters in the Liberman (1977) experiment.
Finally, what is a verbal rehearsal mechanism?